In medical applications an aspiration device is one which applies suction or partial vacuum to draw a fluid or sample into a syringe or into an attached needle lumen. Such devices are particularly useful for securing specimens from palpable and non-palpable lesions found in the thyroid, breast, lymph nodes, prostate, liver, kidney, lung and pancreas for histologic and cytologic examination.
The simplest and most widely used prior art aspirating device is a conventional, plastic hypodermic syringe of the type having a hollow needle opening into a syringe barrel and a plunger for varying the volume and pressure inside the barrel. In use, negative pressure is created by drawing back o the plunger. This required two hands, one to hold the syringe barrel and one to withdraw the plunger. The main disadvantage to using a conventional syringe only as an aspirating device to assist in biopsy, is the necessity to have one hand free to assist in the procedure.
At the present time, biopsy specimens are obtained by surgical excision or by needle biopsy. In needle biopsy, specimens are obtained by any of several techniques, all of which involve applying negative pressure to a syringe with an attached needle.
Where a soft tissue specimen is desired, such as in liver biopsy, continued suction is applied to the needle to assist in severing and retrieving the specimen. This procedure can require two people to perform the biopsy or the use of a syringe device wherein the operator can lock the plunger back in a continuous suction position. (See, e.g., U.S. Pat. Nos. 3,882,849 and 3,938,505 to Jamshidi). One hand control is accomplished, but variable suction is not available or needed for this procedure.
When doing fine or thin needle aspiration biopsy of a nodule, it is necessary to secure or immobilize the mass. This is done with two fingers of one hand, while making multiple sticks with the needle, and at the same time applying suction with the other hand. It is of paramount importance that the operator be able to stop suction and neutralize syringe barrel pressure at precisely the right time.
Prior medical aspiration devices that attempt to provide for single-hand control suffer from disadvantages of being structurally complicated and cumbersome. These are reusable devices that incorporate metal rods, springs and handle assemblies that are coupled to a plastic syringe. These devices place the syringe and attached needle considerably distant from the operator's hand, resulting in potential unsteadiness, and also distant from the patient, resulting in procedure awkwardness and patient anxiety.
In U.S. Pat. No. 4,664,128, a single-hand controlled aspiration device is provided. The device disclosed in U.S. Pat. No. 4,664,128 includes a finger grip member positioned near the proximal end of the syringe and a spring surrounding the external portion of the plunger to bias the plunger outwardly from the syringe barrel. However, due to the outward biasing action of the spring the device is best suited for biopsy procedures other than fine needle aspiration procedures. Since fine needle aspiration with the device described in U.S. Pat. No. 4,664,128 requires specimen collection only in the hub at the distal end of the syringe barrel, the outward biasing of the spring around the plunger unnecessarily complicates control of syringe barrel pressure. Specifically, once a specimen is drawn into the barrel hub a sufficient counterforce must be applied to stop the outward movement of the plunger otherwise, if negative pressure in the barrel is not neutralized, the specimen is aspirated into the syringe handle and artifaction will occur. Alternatively, if the counterforce pressure applied to the plunger is too great the specimen will be prematurely discharged from the syringe barrel.
Accordingly, there is a need for an improved single-hand operated aspiration device for conducting fine needle biopsy procedures.